Downregulation of M Current Is Coupled to Membrane Excitability in Sympathetic Neurons Before the Onset of Hypertension

Neurohumoral activation is an early hallmark of cardiovascular disease and contributes to the etiology of the pathophysiology. Stellectomy has reemerged as a positive therapeutic intervention to modify the progression of dysautonomia, although the biophysical properties underpinning abnormal activity of this ganglia are not fully understood in the initial stages of the disease. We investigated whether stellate ganglia neurons from prehypertensive SHRs (spontaneously hypertensive rats) are hyperactive and describe their electrophysiological phenotype guided by single-cell RNA sequencing, molecular biology, and perforated patch clamp to uncover the mechanism of abnormal excitability. We demonstrate the contribution of a plethora of ion channels, in particular inhibition of M current to stellate ganglia neuronal firing, and confirm the conservation of expression of key ion channel transcripts in human stellate ganglia. We show that hyperexcitability was curbed by M-current activators, nonselective sodium current blockers, or inhibition of Na v 1.1-1.3, Na v 1.6, or I NaP . We conclude that reduced activity of M current contributes significantly to abnormal firing of stellate neurons, which, in part, contributes to the hyperexcitability from rats that have a predisposition to hypertension. Targeting these channels could provide a therapeutic opportunity to minimize the consequences of excessive sympathetic activation.

Identification of NPB, NPW and Their Receptor in the Rat Heart

Members of neuropeptide B/W signaling system have been predominantly detected and mapped within the CNS. In the rat, this system includes neuropeptide B (NPB), neuropeptide W (NPW) and their specific receptor NPBWR1. This signaling system has a wide spectrum of functions including a role in modulation of inflammatory pain and neuroendocrine functions. Expression of NPB, NPW and NPBWR1 in separate heart compartments, dorsal root ganglia (DRG) and stellate ganglia was proven by RT-qPCR, Western blot (WB) and immunofluorescence. Presence of mRNA for all tested genes was detected within all heart compartments and ganglia. The presence of proteins preproNPB, preproNPW and NPBWR1 was confirmed in all the chambers of heart by WB. Expression of preproNPW and preproNPB was proven in cardiac ganglionic cells obtained by laser capture microdissection. In immunofluorescence analysis, NPB immunoreactivity was detected in nerve fibers, some nerve cell bodies and smooth muscle within heart and both ganglia. NPW immunoreactivity was present in the nerve cell bodies and nerve fibers of heart ganglia. Weak nonhomogenous staining of cardiomyocytes was present within heart ventricles. NPBWR1 immunoreactivity was detected on cardiomyocytes and some nerve fibers. We confirmed the presence of NPB/W signaling system in heart, DRG and stellate ganglia by proteomic and genomic analyses.

Resiniferatoxin (RTX) ameliorates acute respiratory distress syndrome (ARDS) in a rodent model of lung injury

Acute lung injury (ALI) is associated with cytokine release, pulmonary edema and in the longer term, fibrosis. A severe cytokine storm and pulmonary pathology can cause respiratory failure due to acute respiratory distress syndrome (ARDS), which is one of the major causes of mortality associated with ALI. In this study, we aimed to determine a novel neural component through cardiopulmonary spinal afferents that mediates lung pathology during ALI/ARDS. We ablated cardiopulmonary spinal afferents through either epidural T1-T4 dorsal root ganglia (DRG) application or intra-stellate ganglia delivery of a selective afferent neurotoxin, resiniferatoxin (RTX) in rats 3 days post bleomycin-induced lung injury. Our data showed that both epidural and intra-stellate ganglia injection of RTX significantly reduced plasma extravasation and reduced the level of lung pro-inflammatory cytokines providing proof of principle that cardiopulmonary spinal afferents are involved in lung pathology post ALI. Considering the translational potential of stellate ganglia delivery of RTX, we further examined the effects of stellate RTX on blood gas exchange and lung edema in the ALI rat model. Our data suggest that intra-stellate ganglia injection of RTX improved pO2 and blood acidosis 7 days post ALI. It also reduced wet lung weight in bleomycin treated rats, indicating a reduction in lung edema. Taken together, this study suggests that cardiopulmonary spinal afferents play a critical role in lung inflammation and edema post ALI. This study shows the translational potential for ganglionic administration of RTX in ARDS.

Direct comparison of cervical and high thoracic spinal cord injury reveals distinct autonomic and cardiovascular consequences

A wide range of spinal cord levels (cervical 8–thoracic 6) project to the stellate ganglia (which provides >90% of sympathetic supply to the heart), with a peak at the thoracic 2 (T2) level. We hypothesize that despite the proximity of the lesions, high thoracic spinal cord injuries (i.e., T2–3 SCI) do not closely mimic the hemodynamic responses recorded with cervical SCI (i.e., C6–7 SCI). To test this hypothesis, rats were instrumented with an intra-arterial telemetry device (Data Sciences International PA-C40) for recording arterial pressure, heart rate, and locomotor activity as well as a catheter within the intraperitoneal space. After recovery, rats were subjected to complete C6–7 spinal cord transection ( n = 8), sham transection ( n = 4), or T2–3 spinal cord transection ( n = 7). After the spinal cord transection or sham transection, arterial pressure, heart rate, and activity counts were recorded in conscious animals, in a thermoneutral environment, for 20 s every minute, 24 h/day for 12 consecutive weeks. After 12 wk, chronic reflex- and stress-induced cardiovascular and hormonal responses were compared in all groups. C6–7 rats had hypotension, bradycardia, and reduced physical activity. In contrast, T2–3 rats were tachycardic. C6–7 rats compared with T2–3 and spinal intact rats also had reduced cardiac sympathetic tonus, reduced reflex- and stress induced cardiovascular responses, and reduced sympathetic support of blood pressure as well as enhanced reliance on angiotensin to maintain arterial blood pressure. Thus injuries above and below the peak level (T2) of spinal cord projections to the stellate ganglia have remarkably different outcomes. NEW & NOTEWORTHY Twelve consecutive weeks of resting hemodynamic data as well as chronic reflex- and stress-induced cardiovascular, autonomic, and hormonal responses were compared in spinal intact and C6–7 and T2–3 spinal cord-transected rats. C6–7 rats compared with T2–3 and spinal intact rats had reduced cardiac sympathetic tonus, reduced reflex- and stress-induced cardiovascular responses, and reduced sympathetic support of blood pressure as well as enhanced reliance on angiotensin to maintain arterial blood pressure. Thus injuries above and below the peak level (T2) of spinal cord projections to the stellate ganglia have remarkably different outcomes.

Surgical Isolation of Stellate Ganglia and Electrophysiology v1

Surgical Isolation of Stellate Ganglia and Electrophysiology